In the examination of a circulatory organ, in order to look at the state of microscopic blood vessels, a contrast medium has been injected into the blood vessels in some cases to take an image. For example, the following method is known, a method of performing a subtraction process on a mask image, which is taken before the contrast medium is injected into the blood vessels, and a contrast image, which is taken with the injected contrast medium, to obtain a subtraction image in which an angiographic portion is enhanced and using the subtraction image as a diagnosis image.
When an image of lower limbs or the like is taken angiographically, the image is, in some cases, taken with stepping DSA (Digital Subtraction Angiography) as a top panel of a bed slides incrementally. However, in the process of making the top panel slide in accordance with the flow of the contrast medium, the timing of sliding could vary depending on how skillful an operator is and other factors. In particular, if the flows of the contrast medium are different in both legs due to the state of narrowed blood vessels, it is difficult to fix the timing to make the top panel slide. Therefore, an appropriate stepping DSA image may not be obtained.
JP-A-06-237924 discloses an X-ray diagnosis apparatus that is designed to move the bed in accordance with the movement of the contrast medium. In the above example, plenty of ROIs are set on an image. Whether the contrast medium flows in is determined based on a change in the average ROI density. The average velocity of the contrast medium passing through N regions is then calculated, and the movement of the bed is controlled based on a result of the calculation.
However, in the above example, the flow of the contrast medium in the patient does not match the slide timing of the bed in such cases as where the velocities of blood flows are different in both legs due to the state of narrowed blood vessels, it may take time to obtain an appropriate image.